Method of making porous articles



Aug. Z5, 1942i. J. T. MARVIN 2,293,843

METHOD OF MAKING POROUS ARTICLES Filed March 2v, 1940 721 Cae/afwr Saa/Pc:

INVENTOR ATTORNEYS atented Aug. 25, 1942 Es PAT:

'r oir-Fica .lohn T.

eral Motos poration or Delaware Application March 27, 1940, Serial No. 326,229

t claims. (Cl. .t9-189) The present invention is directed to a method for making porous metal articles and is particularly concerned with a method of making porous metal articles having varying porosities throughout the cross-section thereof.

It is an object of the invention to provide a method wherein the disposition of metal powder particles of varying grain size is accomplished above object it is a further object to cause said segregation by means of Vibrations produced either by mechanical or electrical means.

Further objects and advantages of the present `invention will be apparent from the following description reference being had to the accompanying drawing wherein preferred embodiments of the present invention is clearly shown.

In the drawing:

Fig. 1 illustrates one form of apparatus which may be used to segregate metal powders.

Fig. 2 shows another type of apparatus for segregating metal powders and Fig. 3 shows an enlarged. fragmentary cross-sectional view of supporting surface with a segregating powder metal layer thereon.

This invention is concerned with a method for producing articles as disclosed in Serial No. 326,235, led March 2'7, 1940, now matured into Patent No. 2,267,918, granted Dec. 30, 1941, wherein porous sheet-like metal articles are disclosed which have different porosity at one side of the sheet than on the other side thereof. That is, the porosity through a cross-section of the porous metal varies. In Serial No. 326,220, led March 27, 1940 assigned to assignee of the present invention, a method is disclosed whereby coarse powder metal particles may be deposited upon a supporting surface and finer metal particles may be deposited thereon for making a particular type of layer. In this invention the disposition of the varying grain size particles is reversed and the nner metal particles are supported directly on the supporting surface and in turn support the coarser metal particles.

To accomplish this disposition in the metal particles, I utilize the segregation thereof whereby thene particles migrate toward the bottom or toward the supporting surface and the coarser particles find their way to the top of the metal powder layer.

In Fig. 1, a cradle ory support 20 is utilized to carry a plate. 22 which may be madeof a nonby means of segregation. In carrying out the adhering material such as graphite, chromium f plated steel, wherein the surface thereof has been cried, or, carrying a refractory-` layer, or a Dayton, ohio, assignor to Gen- Corporation, Detroit, Mich., a corsheet of refractory material. The cradle 2@ has a downwardly extending plunger 24 thereon which is surrounded by a coil Zvwhich in turn is connected to an alternating current source. Thus, when current is supplied to the coil 2t, the cradle 20 is alternately raised upwardly and pulled downwardly, suitable dampening means or limit ing means being provided so that the amplitude of the vibration of the cradle may be controlled. The frequency of vibration and the amplitude is controlled by the frequency and strength of the current and it is also contemplated that in place of the single coil a pair of coils may be provided which are connected to direct current souces of opposite polarities, or a single coil may be used with a direct current source,.wherein reversing polarity is provided. Also an interrupter in the circuit may be used wherein mechanical means are used to cause movement in one direction.'

Metal powder is spread uniformly on the supporting surface or plate 22 and comprises powder of varying grain size, for example, ranging from 80 to 200 mesh. The plate is then vibrated in a single plane, to cause the metal particles to segregate and assume positions as noted in Fig. 3,`

wherein the metal powder layer 28 has the coarse particles 3D supported upon the finer particles 32.

In some cases it may be desirable to bond the metal powder layer directly to the supporting surface for uses such as are contemplated in 'Serial No. 85,297 now matured into Patent No.

2,198,253, assigned to assignee of the present invention. In this instance, the supporting surface 22 mayV be steel, iron, nickel, copper,` or copper plated steel, as the case may be.

VAfter segregation ofthe metal powdered layer, the supporting plate 22 is removed from 'cradle 2@ and placed in a sintering furnace where it is heated under non-oxidizing conditions for a time l and at a temperature suicient to cause the metal powder particles to bond together and form a porous layer having different porosities at either side thereof, after cooling, the porous metal layer may be removed therefrom. When the supporting plate 22 ismade of metal, the porous layer isy bonded thereto.

Fig. 2 illustrates another type of apparatus which maybe used to accomplish the samepurpose as the apparatus in Fig. 1. In this instance, the Vibration of the cradle 20 is accomplished by mechanical means, for example, a rotating cam 3i which actuates the plunger 2li. In this case, the cradle 20 is preferably carried by means of springs 35 attached to a stationary member sov that the cradle 2@ follows the movements of the cam 24. The amplitude of the vibration is coning points of the low melting metal and the high trolled by the eccentricity oi the cam 34 and the' melting metal, such sintering temperatures being frequency of the vibration is controlled by the well-knownin the art.

speed of rotation of cam 24. It is apparent that While the embodiments of the present inventhe apparatus shown in Figs. 1 and 2 is diagram- 5 tion as herein disclosed, constitute preferred matic and may be modified to suit the particular forms, it is to be understood that other forms applicationtowhichitis tobe applied. might be adopted. all coming Within the scope In all of the embodiments the use of preof the claims which follow.

alloyed metal powder is preferred, since segrega- What is claimed is as follows:

tion will occur between powder of varying l 1. A method of making porous metal sheet density, that is tosay, if a bronze layer is dematerial wherein the porosity at one side of the sired, and copper and tin powders are mixed, sheet is different than the porosity at the other the constituent metals themselves will segregate side of the sheet, comprising the steps of, diseven if the grain size is the same. For this reatributing a layer of non-compacted metal powder son it is preferred that the constituent metals l5 upon a supporting surface, said powder includare attached to one another prior to disposition ing particles of different grain sizes, agitating 7of plate Y22. This may be accomplished by prethe supporting surface with the metal powder alloying the metal powder either completely or thereon for causing segregation of the metal incompletely so that a constituent richsurface particles, whereby the smaller particles migrate of the low melting constituent is present on each toward the supporting surface and the larger particle of powder, thus if copper is used, a tin particles, migrate in the opposite direction, and surface is present thereon.'` Powders of this then heating the supporting surface with the type are disclosed in co-pending application Semetal powder thereon for sintering the metal rial No. 322,753, assigned to assignee of the powder together, into a strong porous structure present invention. which has a different porosity at one side thereof The particular metal powders to be used are than at the other side of said sheet.

of slight importance and may include pure cop- 2. The method as defined in claim l, wherein per, pure nickel, pure iron or the powder may the agitation is accomplished by mechanical be .pre-alloyed particles including copper-nickel, means. copper-tin, iron-copper, nickel-tin, copper-tin- 3. The method as defined in claim 1 wherein antimony, etc. It is to be understood that the the agitation is accomplished by electrical particular metal powder used is of little impormeans. tance and forms no part of this invention. 4. The method as claimed in claim 1, wherein For illustrative purposes only the following the agitation is accomplished bykmeans of vibraexarnple is given to show that preferred times tion in one plane only. and temperatures used during the sintering 5. The methodI of making composite sheet process. Metal powder particles ranging from material wherein a porous metal layer having 80 to 200 range are provided with a composition a different porosity at one side thereof than at of 90% copper and 10% tin, the tin being in the other side is bonded to a supporting surface the form of a constituent rich surface on the of a more dense metal, comprising the steps of, copper particles, these particles are disposed distributing a non-compacted layer of metal upon a plate 22 of graphite in a uniform layer powder having a different grain size upon the and are then segregated thereon by means of surface of a more dense metal support and then vibrating the plate in cradle 20. The plate with vibrating the support for causing segregation of the segregated layer thereon is then placed in a i5 the metal particles whereby the finer metal sintering furnace and heated for a period of particles migrate toward the more dense metal from 10 to 20 minutes according to the degree of supporting surface and the coarser particles mialloying desired at temperatures from 1500 to grate away from said surface, and then heating 1800 C. The sintering step is carried out under the more dense metal supporting surface with non-oxidizing conditions and the metal powder so the segregated powder metal layer thereon under particles become bonded together at their connon-oxidizing conditions and fora time and at tacting surfaces and form a porous layer having a temperature sufficient to cause the powder different porosities at either side thereof, due to metal particles to sinter together into a strong the different grain size powders which have beporous layer having less porosity at the side come segregated upon the supporting plate. adjacent the supporting surface than at the other After cooling, which is preferably carried out side thereof and simultaneously causing the under non-oxidizing conditions, the porous plate porous layer to bond in situ to the supporting maybe-liftedrfrompthe spporting-surfaceand Surface.

put to its specific use. mediorgaking a metal powder While the disclosure has been directed to prelayer having a diiferent\presity at one side alloying powders when two or more metals are thereof than at the other side, meire used, it is apparent that if the metal powder vibrating a layer of metal powder of varying constituents are not of greatly dierent density, grain size upon a supporting surface for a time that the pre-alloyingr is unnecessary, this consufficient to cause the metal powder particles dition being best determined by experiment. 5 0f different grain size to segregate upon the sup- Sintering temperatures, when using pure porting surface whereby the porosity of the layer metal powders, should be held slightly below the adjacent the supporting surface is less than the melting point of the metal, while when utilizing porosity at the other side of the layer. pre-alloyed metal powders, the sintering temperatures should be held intermediate the melt- JOHN T. MARVIN.

CERTI FICATE OF CO RRECTION Patent No. 2,295,8LL5. August 25, 19kg.

JOHN T. MARVIN.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, first Column, iinel, for 18000 c. read --1800o F.; and that the'said Letters Patent should be read with this correction therein that the same may conform to the rec-ord of the case in the Patent Office.

Signed and sealed this 10th day of November, A. D. 19li2.

Henry Van Arsdale,

Acting Commissioner of Patents (Seal) CERTI FIXCATE OF CO RRECT ION Patent No. 2,295,8h5. August 25, 19kg.

JOHN T. MARVIN.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, first column, lnelQ, foi "18000 C. :read` -18000 F.-; -and that the '.sad Letters Patent shouldbe read with this correction therein that thesame may confom to the reeord of the case in the Patent Office. y

Signed and sealed this 10th day of November, A. D. 1914.2.

Henry Van Arsdale, (Seal) Acting Commissioner of Patents. 

